1. Field of the Invention
The present invention relates to rotary anode X-ray tubes, and in particular to such X-ray tubes wherein the anode is connected at one end of a shaft which is magnetically mounted within the X-ray tube at its opposite end.
2. Description of the Prior Art
A rotory anode tube wherein the anode member is mounted at one end of a shaft which is magnetically mounted at its opposite end within the X-ray tube is described, for example, in British Pat. No. 1,595,406. In conventional rotary anode X-ray tubes of this type, the driving connection between the drive means and the anode shaft is effected by means of a cup or sleeve which is in turn rigidily connected to the anode shaft. The sleeve or cup also has at least one stop bearing for emergency support of the shaft in the event of the magnetic mounting means ceasing to operate for the purpose of limiting movement of the anode and shaft so as to avoid impact of the shaft and/or anode against the immobile parts of the X-ray tube.
A problem in the design of emergency support means such as the stop bearings in conventional X-ray tubes is that the bearings provide substantially one-sided support for the anode and shaft resulting in an extremely high torque due to the relatively long lever-arm which must be supported by the stop bearing. This is a particularly acute problem in the case of X-ray tubes exhibiting a high anode rotational speed, in the range of 200 Hz or greater.